The present invention relates to a cut point detection system for detecting the cut point in the moving picture compressed data, a shot identification system for identifying the contents of a shot partitioned by this cut point detection system, a cut point detection method, and a cut point detection program.
In recent years, the terrestrial digital broadcasting and the Internet broadcasting have begun to spread into the ordinary households, and as the computer technologies, particularly, the storage technologies, have rapidly expanded, an HDD recorder with a storage device having a capacity of terabytes, which was unthinkable several years ago, has been available on the market.
In this situation, there is not only a conventional way of enjoyment in which many programs (contents) are recorded beforehand, and when one wants to see a program, one sees it, but also there has been a growing interest in the multi-media database having a high edit function of automatically retrieving only a desired spot (scene) from an enormous number of contents, or automatically creating a highlight scene in which only the scenes of special note are collected from a long time program such as a sports program.
One of the basic technologies for realizing this multi-media database needs an operation of dividing one video contents into scenes, and reconstructing them. That is, a method for automatically making an operation of specify the data position where the scene changes, and classifying each scene according to its contents, namely, video indexing, is required.
Conventionally, the invention of this kind is a hierarchical mixed type shot conversion detection method in the MPEG compressed video environment as described in patent document 1, for example.
In this invention, first of all, a scene candidate section is detected using a difference in the overall color distribution between I frames by applying a shot detection algorithm based on the color histogram. The P frame within each detected candidate section is additionally decoded. A reduced shot conversion candidate section is obtained using a difference in the overall color histogram between adjacent I/P, P/P or P/I frames. For the shot conversion candidate section, each B frame within the section is decoded at macro-block level to obtain a distribution characteristic of the intra-coding block and the reference type and reference pattern of each B frame, and detect an instantaneous cut point, using them.
As another prior art, a cut point detection method as described in non-patent document 1 involves firstly detecting a GOP (Group Of Picture) containing the cut point, using DC image information of I frame (refer to non-patent document 1:3.1.1 I method).
Subsequently, for the GOP judged that the cut point is contained through the above process, the cut point position is detected on a frame basis, using an MBT (Macro Block Type) (refer to non-patent document 1:3.1.2 MBT method), and to decrease the detected points, for each B frame pair (Bi, Bi+1) in the GOP,Δ=|fi−bi|+|fi+1−bi+1|
(fi, fi+1: number of forward predictive MBT, bi, bi+1: number of backward predictive MBT)
is computed, whereby the B frame pair taking the maximum value Δmax is obtained, and when the ratio of the value taken by another frame to Δmax is less than or equal to a predetermined threshold value TΔ, it is judged that the cut point occurs.
And with this prior art, the instantaneous cut point is successfully detected at a high detection ratio of 90% or more through the gradual process.
However, in the former prior art, the gradual detection process of detecting the candidate section and detecting the cut point in the candidate section is required, and a multiplicity of decoding processes including the process for decoding the P frame and the process for decoding the B frame at macro block level are required, and take a lot of time.
Also, in the latter prior art, the gradual process including the rough detection on a GOP basis using the DC image and the detection of B frame using the feature of macro block type is required, and the arithmetic operation process taking a relatively long processing time is required to improve the detection precision, whereby there is a scope for improvement to simplify the process or shorten the overall processing time by increasing the speed.
Also, in any of the former and latter processes, after the cut point is detected, the contents of video for the shot partitioned by the cut point can not be identified
[Patent Document 1]
Japanese Patent Publication No. 2001-313956A
[Non-Patent Document 1]
“Detecting the cut point of MPEG2 compressed moving picture using Macro Type Block”, Information Processing Society of Japan, Collected papers: Computer Vision and Image Media, Vol. 46, No. SIG15 (CVIM12), pp. 51-58, October 2005.